Biden: Helen Clark 'closely considered' for UN top job

US Vice President Joe Biden says Helen Clark is being "closely considered" as she makes her bid for the United Nations Secretary-General.

During his historic short visit to New Zealand on Thursday, Mr Biden said Prime Minister John Key had done a great job in pushing Ms Clark's case.

US Vice President Joe Biden and Prime Minister John Key (Getty)

"I said somewhat humorously that I wish we had the non-partisan zeal you have. If the potential nominee for the United Nations Secretary-General could hear what the opposition had to say... I was impressed. I thought she was his sister.

"All kidding aside, we have a very high regard for your nominee and she is one who is being closely considered."

Mr Key has been pushing for his prime ministerial predecessor's cause during meetings with other world leaders.

The successful candidate needs the backing of the Security Council including the five permanent members the US, UK, Russia, France and China whose selection will be a secret.

In a joint news conference with Mr Key at Government House in Auckland on Thursday, Mr Biden also called New Zealand an "incredibly valuable partner" on the Security Council and in the fight against Islamic State.

During his comments, Mr Biden also confirmed the visit of a US ship to the Royal New Zealand Navy's 75th anniversary celebrations ending a 30-year stalemate over the nuclear-free policy.

Before his official welcome at Government House, Mr Biden met with two All Blacks which he joked was the real reason for his trip to New Zealand.